镉胁迫对紫花苜蓿镉吸收特征及根系形态影响

采用盆栽模拟方法,研究了4种镉(Cd)浓度(0,10,25,50 mg/kg)下紫花苜蓿对Cd吸收特征及根系形态的变化特征。结果发现,随着镉胁迫加剧,紫花苜蓿地上生物量、根系生物量、根系总长度、根平均直径、根表面积、根系体积、根尖数和分枝数均显著下降(P<0.05),地上部生物量分别为对照的87.8%,56.5%,14.3%,根系生物量分别为96.1%,63.3%,16.2%;不同部位镉吸收量表现为细根>地上部>粗根,三者均随着处理浓度增加而显著提高,细根镉含量与地上部镉含量呈显著正相关;地上部最高镉积累量出现在25 mg/kg处理中,达到7.715 μg/株;不同径级根系的总根长、根表面积、根体积随镉浓度增加呈下降趋势,根径<0.5 mm根系占总根系比例呈增加趋势。研究表明,紫花苜蓿可用于低Cd污染场地的植被恢复,其根系对Cd胁迫的响应特征呈现侧根产生—根受损的动态平衡现象。

Cadmium uptake and root morphological changes in Medicago sativa under cadmium stress

This study used pot experiments to investigate the cadmium (Cd)uptake potential of alfalfa (Medi-cago sativa )and to explore the possible mechanisms involved in root adaptation under various levels of cadmi-um stress (0,10,25,50 mg/kg).Alfalfa shoot biomass,root biomass,total root length,root surface-area, root volume,average root diameter and root number were all significantly smaller under the three Cd stress treatments than in the normal Cd condition (P <0.05).Shoot biomass was 87.8%,56.5% and 14.3%,and root biomass was 96.1%,63.3% and 16.2% respectively.The highest Cd content was observed in fine roots (root diameter below 1.0 mm)and the Cd content in shoots was higher than that in roots with diameters above 1.0 mm.The Cd content in three parts (shoot,fine root,coarse root)increased significantly with increasing Cd exposure.The highest Cd accumulation was recorded in shoots (7.715 μg/plant)at a concentration of 25 mg/kg Cd.Compared to the control,root length,root surface-area and the root volume of different diameter classes decreased significantly with increases in Cd concentration,except for the proportion of roots with diam-eters below 0.5 mm,which increased.It can be concluded that alfalfa is suitable for remediation of Cd polluted soil when Cd concentrations are less than 25 mg/kg and the response characteristics of root systems to Cd showdynamic equilibrium.